CN109239513B - Phase selection method for single-phase earth fault of generator stator winding - Google Patents

Phase selection method for single-phase earth fault of generator stator winding Download PDF

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CN109239513B
CN109239513B CN201810554902.8A CN201810554902A CN109239513B CN 109239513 B CN109239513 B CN 109239513B CN 201810554902 A CN201810554902 A CN 201810554902A CN 109239513 B CN109239513 B CN 109239513B
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phase
fault
voltage
mab
zero sequence
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CN109239513A (en
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贾文超
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North China Electric Power University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections

Abstract

The invention discloses a phase selection method for a generator stator winding single-phase earth fault, which measures the three-phase voltage and the zero-sequence voltage of a fault generator; calculating the line voltage of the AB phase by using the three-phase voltage of the generator; calculating a zero sequence voltage break variable, and calculating a phase angle between the zero sequence voltage break variable and the voltage of the AB phase line; and realizing fault phase selection by utilizing the zero sequence voltage phase characteristics and the fault point grounding resistance measured value. The method has the beneficial effect that the phase selection of the single-phase earth fault of the stator is realized by utilizing the phase characteristics and the earth resistance value of the zero-sequence voltage after the fault. The method can realize accurate phase selection of the single-phase earth fault of the stator of the large-scale generator in various neutral point grounding modes, and is suitable for high-resistance earth faults.

Description

Phase selection method for single-phase earth fault of generator stator winding
Technical Field
The invention belongs to the technical field of generators, and relates to a method for accurately selecting a phase of a single-phase earth fault of a stator of a large-scale generator.
Background
The stator winding single-phase earth fault is one of common faults of the generator, and the large generator stator winding has large distributed capacitance, so that the burning of a stator core can be caused and the stator core is expanded into an interphase or turn-to-turn fault. The accurate phase selection of the stator single-phase earth fault is the basis of fault location, and a basis can be provided for quick fault maintenance.
Aiming at a neutral point direct grounding system, a mature phase selection method applied in engineering mainly comprises current mutation phase selection and sequence component phase selection, but a generator is a neutral point indirect grounding system, and the phase selection method is not suitable. At present, a phase selection method of a single-phase earth fault of a stator mainly adopts low-voltage phase selection, namely, a phase with the lowest terminal voltage at the moment of the fault is a fault phase. However, when the stator winding is failed to ground via a high resistance, the failed phase voltage is not necessarily the lowest. The phase selection method aiming at the high-resistance ground fault has yet to be further researched due to the defect of mistaken phase selection when the high-resistance ground fault occurs by using the low-voltage phase selection method.
Disclosure of Invention
The invention aims to provide a phase selection method for a single-phase ground fault of a generator stator winding. The method can realize accurate phase selection of the single-phase earth fault of the stator of the large-scale generator in various neutral point grounding modes, and is suitable for high-resistance earth faults.
The technical scheme adopted by the invention is carried out according to the following steps:
a. measuring three-phase voltage of a faulted generator
Figure BDA0001682039770000011
And
Figure BDA0001682039770000012
and zero sequence voltage
Figure BDA0001682039770000013
b. Calculating line voltage using three-phase voltage of generator
Figure BDA0001682039770000014
c. Using post-fault zero sequence voltage
Figure BDA0001682039770000015
And zero sequence voltage in normal operation
Figure BDA0001682039770000016
Calculating the sudden change of zero sequence voltage
Figure BDA0001682039770000017
And calculating the zero sequence voltage break variable
Figure BDA0001682039770000018
And line voltage
Figure BDA0001682039770000019
Phase angle phi betweenmABAccording to the phase angle phimABThe range of (2) realizes fault phase selection.
Further, zero sequence voltage mutation
Figure BDA0001682039770000021
The expression of (a) is:
Figure BDA0001682039770000022
in the formula CGΣα represents the number of turns of the stator winding from the fault position to the neutral point as a percentage of the total number of turns of the winding;
Figure BDA0001682039770000023
is a fault phase potential;
Figure BDA0001682039770000024
winding electromotive force from a fault point to a neutral point; rfA ground resistor for a fault point; z represents the ground impedance of the neutral point;
zero sequence voltage sudden change when phase A is grounded
Figure BDA0001682039770000025
And line voltage
Figure BDA0001682039770000026
Phase angle phi ofmABThere are the following relationships between:
Figure BDA0001682039770000027
substituting formula (1) into formula (2) to obtain:
Figure BDA0001682039770000028
for large generators, phimABIs related to the phase angle of the winding potential and the fault resistance, and phi is determined by the formula (3) when the phase A is grounded and has faultmABThe angular range of (c).
Further, according to the phase angle phimABThe method for realizing fault phase selection in the range of (1) is as follows:
1) when in use
Figure BDA0001682039770000029
When, it indicates that A is grounded;
2) when in use
Figure BDA00016820397700000210
When, it indicates that B is grounded;
3) when in use
Figure BDA00016820397700000211
Indicating that C is grounded.
Further, when only phi is utilizedmABWhen the fault phase selection can not be realized, the grounding resistance value R measured by using the injection type stator grounding protectionfAnd phimABFault phase selection is realized together.
Drawings
FIG. 1 is a generator stator single phase ground fault schematic;
fig. 2 is a schematic diagram of a large generator stator single-phase earth fault phase selection device.
Detailed Description
The present invention will be described in detail with reference to the following embodiments.
The invention utilizes zero sequence voltage and line voltage
Figure BDA0001682039770000031
Phase difference characteristic fault phase selection method, as shown in FIG. 1, assuming that generator A phase stator winding has a ground fault, α represents the number of stator winding turns from fault location to neutral point as a percentage of the total number of winding turnsA、CBAnd CCThe capacitance to ground of the three-phase stator windings of generator A, B, C are shown separately, assuming for simplicity of analysis that the distributed capacitance of the generator is concentrated at the machine terminals.
Figure BDA0001682039770000032
And
Figure BDA0001682039770000033
electromotive forces respectively representing three phases of the generator stator A, B, C;
Figure BDA0001682039770000034
the winding electromotive force from the fault point to the neutral point, theta is the phase angle at which the winding potential leads the phase potential,
Figure BDA0001682039770000035
is the ground current of the fault point. RfA ground resistor for a fault point; z represents the grounding impedance of the neutral point, the value of which is grounded to the neutral point of the generatorThe way is relevant. Phi is amIndicating a faulty phase potential
Figure BDA0001682039770000036
The phase angle of (c).
The fault phase selection method comprises the following steps:
step 1: measuring machine-end three-phase voltage by using generator terminal voltage transformer
Figure BDA0001682039770000037
And
Figure BDA0001682039770000038
and zero sequence voltage
Figure BDA0001682039770000039
Step 2: calculating line voltage using three-phase voltage of generator
Figure BDA00016820397700000310
And step 3: using post-fault zero sequence voltage
Figure BDA00016820397700000311
And zero sequence voltage in normal operation
Figure BDA00016820397700000312
Calculating the sudden change of zero sequence voltage
Figure BDA00016820397700000313
And calculating the zero sequence voltage break variable
Figure BDA00016820397700000314
And line voltage
Figure BDA00016820397700000315
Phase angle phi betweenmAB。
After single-phase earth fault of stator winding, zero sequence voltage sudden change amount
Figure BDA00016820397700000316
The expression of (a) is:
Figure BDA00016820397700000317
in the formula CGΣ-total capacitance of the generator three with respect to ground;
zero sequence voltage sudden change when phase A is grounded
Figure BDA00016820397700000318
And line voltage
Figure BDA00016820397700000319
Phase angle phi ofmABThere are the following relationships between:
Figure BDA0001682039770000041
the formula (1) can be substituted for the formula (2):
Figure BDA0001682039770000042
for large generators, phimABIs related to the phase angle of the winding potential and the fault resistance, and phi is determined by the formula (3) when the phase A is grounded and has faultmABThe angular range of (c).
And 4, step 4: using phimABAnd fault point ground resistance measurement value RfRealizing fault phase selection:
1) when in use
Figure BDA0001682039770000043
When, it indicates that A is grounded;
2) when in use
Figure BDA0001682039770000044
When, it indicates that B is grounded;
3) when in use
Figure BDA0001682039770000045
Time, showAnd the phase C is grounded.
Using only said phimABWhen the fault phase selection can not be realized, the grounding resistance value R measured by using the injection type stator grounding protectionfAnd phimABFault phase selection is realized together.
To be provided with
Figure BDA0001682039770000046
For example, when Rf≥RsetIf not, the phase A is grounded.
The schematic diagram of a single-phase earth fault positioning device of a large salient pole generator stator is shown in fig. 2, and the device comprises a generator 1, a voltage transformer 2 and a generator protection device 3. The method for realizing the fault phase selection comprises the following steps: after the three-phase voltage and the zero-sequence voltage at the generator end are measured by using the voltage transformer 2, the break variable of the zero-sequence voltage is calculated
Figure BDA0001682039770000047
And line voltage
Figure BDA0001682039770000048
Finally calculating the zero sequence voltage mutation
Figure BDA0001682039770000049
And line voltage
Figure BDA00016820397700000410
Phase angle phi betweenmABAnd the fault phase selection is realized by combining with the grounding resistance value. The invention provides a phase selection method suitable for high-resistance grounding faults, which realizes accurate phase selection of a large-scale generator and provides reliable basis for quick fault maintenance.
The invention has the following characteristics:
1. the traditional stator earth fault phase selection research mainly utilizes amplitude characteristics of phase voltage, changes of phase characteristics of zero-sequence voltage after faults are ignored, and the invention provides a method for realizing faults by utilizing the phase characteristics of the zero-sequence voltage.
2. The method is suitable for various neutral point grounding modes, and the fault phase can be accurately selected when high-resistance grounding faults occur.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not intended to limit the present invention in any way, and all simple modifications, equivalent variations and modifications made to the above embodiments according to the technical spirit of the present invention are within the scope of the present invention.

Claims (1)

1. A phase selection method for a generator stator winding single-phase earth fault is characterized by comprising the following steps:
a. measuring three-phase voltage of a faulted generator
Figure FDA0002532668810000011
And
Figure FDA0002532668810000012
and zero sequence voltage
Figure FDA0002532668810000013
b. Calculating line voltage using three-phase voltage of generator
Figure FDA0002532668810000014
c. Using post-fault zero sequence voltage
Figure FDA0002532668810000015
And zero sequence voltage in normal operation
Figure FDA0002532668810000016
Calculating the sudden change of zero sequence voltage
Figure FDA0002532668810000017
And calculating the zero sequence voltage break variable
Figure FDA0002532668810000018
And line voltage
Figure FDA0002532668810000019
Phase angle phi betweenmABAccording to the phase angle phimABThe range of (2) realizes fault phase selection;
zero sequence voltage break variable
Figure FDA00025326688100000110
The expression of (a) is:
Figure FDA00025326688100000111
in the formula CGΣα represents the number of turns of the stator winding from the fault position to the neutral point as a percentage of the total number of turns of the winding;
Figure FDA00025326688100000112
is a fault phase potential;
Figure FDA00025326688100000113
winding electromotive force from a fault point to a neutral point; rfA ground resistor for a fault point; z represents the ground impedance of the neutral point;
zero sequence voltage sudden change when phase A is grounded
Figure FDA00025326688100000114
And line voltage
Figure FDA00025326688100000115
Phase angle phi ofmABThere are the following relationships between:
Figure FDA00025326688100000116
substituting formula (1) into formula (2) to obtain:
Figure FDA00025326688100000117
for large generators, phimABIs related to the phase angle of the winding potential and the fault resistance, and phi is determined by the formula (3) when the phase A is grounded and has faultmABThe angular range of (d);
according to the phase angle phimABThe method for realizing fault phase selection in the range of (1) is as follows:
1) when in use
Figure FDA0002532668810000021
When, it indicates that A is grounded;
2) when in use
Figure FDA0002532668810000022
When, it indicates that B is grounded;
3) when in use
Figure FDA0002532668810000023
When, indicates that C is grounded;
when only said phi is utilizedmABWhen the fault phase selection can not be realized, the grounding resistance value R measured by using the injection type stator grounding protectionfAnd phimABJointly realize fault phase selection when Rf≥RsetIf not, the phase A is grounded.
CN201810554902.8A 2018-06-01 2018-06-01 Phase selection method for single-phase earth fault of generator stator winding Expired - Fee Related CN109239513B (en)

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CN110261722B (en) * 2019-08-06 2021-02-02 云南电网有限责任公司电力科学研究院 Single-phase grounding judgment and phase judgment method of neutral point ungrounded system
CN112180290B (en) * 2020-09-29 2024-03-08 西安热工研究院有限公司 Positioning method for generator stator ground fault
CN113281648B (en) * 2021-05-12 2022-11-01 华中科技大学 Method and system for positioning ground fault of generator stator of marine nuclear power platform
CN113820620A (en) * 2021-08-17 2021-12-21 捍防（深圳）实业有限公司 Fault analysis method and fault analysis device for power supply system

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